A fitness process is better than a fitness program
You need a process for improving your fitness training, not just an exercise program.
Your weekly schedule shouldn’t be static. You should constantly be making small changes and tweaks. It’s good to make adjustments based on your current fatigue. It’s also good to play around with small modifications—going a bit faster, adding more rest time, adding a bit more weight.
The majority of what you do should look similar on a week-to-week basis. Mostly, you should follow the plan. But there should always be some change and experimentation.
The younger your training age, the more room for experimentation. You don’t know what works for you yet.
If you’re just getting started, then start with a program. It will quickly get you to a pretty good place. But view this as your first experiment, rather than as the plan you must continue to follow.
Ask yourself, how will I test to see if this program is working? What adjustments could I make to try and get a better training stimulus? In light of my current fatigue, how should I change the plan for today?
A well-written program will be better at first. But a well-constructed process generates mastery.